# -*- coding: utf-8 -*-
#
# libcaca Colour ASCII-Art library
# Python language bindings
# Copyright (c) 2010 Alex Foulon <alxf@lavabit.com>
# All Rights Reserved
#
# This library is free software. It comes without any warranty, to
# the extent permitted by applicable law. You can redistribute it
# and/or modify it under the terms of the Do What the Fuck You Want
# to Public License, Version 2, as published by Sam Hocevar. See
# http://www.wtfpl.net/ for more details.
#
""" Libcaca Python bindings """
import ctypes
import errno
from caca import _lib, utf8_to_utf32, utf32_to_utf8
from caca import _PYTHON3, _str_to_bytes, _bytes_to_str
from caca.font import _Font
class _CanvasStruct(ctypes.Structure):
pass
class _Canvas(object):
""" Model for Canvas objects.
"""
def __init__(self):
self._cv = None
def from_param(self):
""" Required by ctypes module to call object as parameter of
a C function.
"""
return self._cv
def __str__(self):
return "<CacaCanvas %dx%d>" % (self.get_width(), self.get_height())
def __del__(self):
if self._cv and _lib is not None:
self._free()
def _free(self):
""" Free a libcaca canvas.
"""
_lib.caca_free_canvas.argtypes = [_Canvas]
_lib.caca_free_canvas.restype = ctypes.c_int
return _lib.caca_free_canvas(self)
class Canvas(_Canvas):
""" Canvas object, methods are libcaca functions with canvas_t as
first parameter.
"""
def __init__(self, width=0, height=0, pointer=None):
""" Canvas constructor.
width -- the desired canvas width
height -- the desired canvas height
pointer -- pointer to libcaca canvas
"""
_lib.caca_create_canvas.argtypes = [ctypes.c_int, ctypes.c_int]
_lib.caca_create_canvas.restype = ctypes.POINTER(_CanvasStruct)
if pointer is None:
try:
self._cv = _lib.caca_create_canvas(width, height)
except ctypes.ArgumentError:
self._cv = 0
raise CanvasError("Specified width or height is invalid")
else:
if self._cv == 0:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Specified width or height is"
" invalid")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory for the requested"
" canvas size")
else:
raise CanvasError("Unknown error: failed to create"
" canvas")
else:
self._cv = pointer
def manage(self, *args, **kw):
""" Not implemented.
"""
raise CanvasError("Not implemented")
def unmanage(self, *args, **kw):
""" Not implemented.
"""
raise CanvasError("Not implemented")
def set_size(self, width, height):
""" Resize a canvas.
width -- the desired canvas width
height -- the desired canvas height
"""
_lib.caca_set_canvas_size.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int
]
_lib.caca_set_canvas_size.restype = ctypes.c_int
try:
ret = _lib.caca_set_canvas_size(self, width, height)
except ctypes.ArgumentError:
raise CanvasError("Specified width or height is invalid")
else:
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Specified width or height is invalid")
elif err.value == errno.EBUSY:
raise CanvasError("The canvas is in use by a display driver"
" and cannot be resized")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory for the requested"
" canvas size")
else:
return ret
def get_width(self):
""" Get the canvas width.
"""
_lib.caca_get_canvas_width.argtypes = [_Canvas]
_lib.caca_get_canvas_width.restype = ctypes.c_int
return _lib.caca_get_canvas_width(self)
def get_height(self):
""" Get the canvas height.
"""
_lib.caca_get_canvas_height.argtypes = [_Canvas]
_lib.caca_get_canvas_height.restype = ctypes.c_int
return _lib.caca_get_canvas_height(self)
def get_chars(self, *args, **kw):
""" Not implemented.
"""
raise CanvasError("Not implemented")
def get_attrs(self, *args, **kw):
""" Not implemented.
"""
raise CanvasError("Not implemented")
def gotoxy(self, x, y):
""" Set cursor position. Setting the cursor position outside the canvas
is legal but the cursor will not be shown.
x -- X cursor coordinate
y -- Y cursor coordinate
"""
_lib.caca_gotoxy.argtypes = [_Canvas, ctypes.c_int, ctypes.c_int]
_lib.caca_gotoxy.restyoe = ctypes.c_int
try:
ret = _lib.caca_gotoxy(self, x, y)
except ctypes.ArgumentError:
raise CanvasError("specified coordinate X or Y is invalid")
else:
return ret
def wherex(self):
""" Get X cursor position.
"""
_lib.caca_wherex.argtypes = [_Canvas]
_lib.caca_wherex.restype = ctypes.c_int
return _lib.caca_wherex(self)
def wherey(self):
""" Get Y cursor position.
"""
_lib.caca_wherey.argtypes = [_Canvas]
_lib.caca_wherey.restype = ctypes.c_int
return _lib.caca_wherey(self)
def put_char(self, x, y, ch):
""" Print an ASCII or Unicode character. Return the width of the
printed character: 2 for a fullwidth character, 1 otherwise.
x -- X coordinate
y -- Y coordinate
ch -- the character to print
"""
_lib.caca_put_char.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, ctypes.c_uint32
]
_lib.caca_put_char.restype = ctypes.c_int
if not isinstance(ch, str):
raise CanvasError("Specified character is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
try:
ret = _lib.caca_put_char(self, x, y, ch)
except ctypes.ArgumentError:
raise CanvasError("specified coordinate X or Y is invalid")
else:
return ret
def get_char(self, x, y):
""" Get the Unicode character at the given coordinates.
x -- X coordinate
y -- Y coordinate
"""
_lib.caca_get_char.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int
]
_lib.caca_get_char.restype = ctypes.c_uint32
try:
ch = _lib.caca_get_char(self, x, y)
except ctypes.ArgumentError:
raise CanvasError("specified coordinate X or Y is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf32_to_utf8(ch)
return ch
def put_str(self, x, y, s):
""" Print a string.
x -- X coordinate
y -- Y coordinate
s -- the string to print
"""
_lib.caca_put_str.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, ctypes.c_char_p
]
_lib.caca_put_str.restype = ctypes.c_int
if _PYTHON3 and isinstance(s, str):
s = _str_to_bytes(s)
try:
ret = _lib.caca_put_str(self, x, y, s)
except ctypes.ArgumentError:
raise CanvasError("Invalid argument")
else:
return ret
def printf(self, x, y, fmt, *args):
""" Print a formated string.
x -- X coordinate
y -- Y coordinate
fmt -- the format string to print
args -- Arguments to the format string
"""
_lib.caca_printf.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, ctypes.c_char_p
]
_lib.caca_printf.restype = ctypes.c_int
if _PYTHON3 and isinstance(fmt, str):
fmt = _str_to_bytes(fmt)
if _PYTHON3:
nargs = []
for arg in args[:]:
if isinstance(arg, str):
nargs.append(_str_to_bytes(arg))
else:
nargs.append(arg)
else:
nargs = args
try:
ret = _lib.caca_printf(self, x, y, fmt, *nargs)
except ctypes.ArgumentError:
raise CanvasError("Specified coordinate X or Y is invalid")
else:
return ret
def vprintf(self, *args, **kw):
""" Not implemented.
"""
raise CanvasError("Not implemented")
def clear(self):
""" Clear the canvas.
"""
_lib.caca_clear_canvas.argtypes = [_Canvas]
_lib.caca_clear_canvas.restype = ctypes.c_int
return _lib.caca_clear_canvas(self)
def set_handle(self, x, y):
""" Set cursor handle. Blitting method will use the handle value to
put the canvas at the proper coordinates.
x -- X handle coordinate
y -- Y handle coordinate
"""
_lib.caca_set_canvas_handle.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int
]
_lib.caca_set_canvas_handle.restype = ctypes.c_int
try:
ret = _lib.caca_set_canvas_handle(self, x, y)
except ctypes.ArgumentError:
raise CanvasError("Specified coordinate X or Y is invalid")
else:
return ret
def get_handle_x(self):
""" Get X handle position.
"""
_lib.caca_get_canvas_handle_x.argtypes = [_Canvas]
_lib.caca_get_canvas_handle_x.restype = ctypes.c_int
return _lib.caca_get_canvas_handle_x(self)
def get_handle_y(self):
""" Get Y handle position.
"""
_lib.caca_get_canvas_handle_y.argtypes = [_Canvas]
_lib.caca_get_canvas_handle_y.restype = ctypes.c_int
return _lib.caca_get_canvas_handle_y(self)
def blit(self, x, y, cv, mask=None):
""" Blit canvas onto another one.
x -- X coordinate
y -- Y coordinate
cv -- the source canvas
mask -- the mask canvas
"""
_lib.caca_blit.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, _Canvas, _Canvas
]
_lib.caca_blit.restype = ctypes.c_int
if not isinstance(cv, Canvas):
raise CanvasError("Specified mask canvas is invalid")
else:
if mask is None:
mask = NullCanvas()
else:
if not isinstance(mask, _Canvas):
raise CanvasError("Specified mask canvas is invalid")
try:
ret = _lib.caca_blit(self, x, y, cv, mask)
except ctypes.ArgumentError:
raise CanvasError("Specified coordinate X or Y is invalid")
else:
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("A mask was specified but the mask size"
" and source canvas size do not match")
else:
return ret
def set_boundaries(self, x, y, width, height):
""" Set a canvas' new boundaries.
x -- X coordinate of the top-left corner
y -- Y coordinate of the top-left corner
width -- width of the box
height -- height of the box
"""
_lib.caca_set_canvas_boundaries.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, ctypes.c_int, ctypes.c_int
]
_lib.caca_set_canvas_boundaries.restype = ctypes.c_int
try:
ret = _lib.caca_set_canvas_boundaries(self, x, y, width, height)
except ctypes.ArgumentError:
raise CanvasError("Specified coordinate or size is invalid")
else:
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Specified width or height is invalid")
elif err.value == errno.EBUSY:
raise CanvasError("The canvas is in use by a display driver"
" and cannot be resized")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory for the requested"
" canvas size")
else:
return ret
def disable_dirty_rect(self):
""" Disable dirty rectangles.
"""
_lib.caca_disable_dirty_rect.argtypes = [_Canvas]
_lib.caca_disable_dirty_rect.restype = ctypes.c_int
return _lib.caca_disable_dirty_rect(self)
def enable_dirty_rect(self):
""" Enable dirty rectangles.
"""
_lib.caca_enable_dirty_rect.argtypes = [_Canvas]
_lib.caca_enable_dirty_rect.restype = ctypes.c_int
ret = _lib.caca_enable_dirty_rect(self)
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Dirty rectangles were not disabled")
else:
return ret
def get_dirty_rect_count(self):
""" Get the number of dirty rectangles in the canvas.
"""
_lib.caca_get_dirty_rect_count.argtypes = [_Canvas]
_lib.caca_get_dirty_rect_count.restype = ctypes.c_int
return _lib.caca_get_dirty_rect_count(self)
def get_dirty_rect(self, idx):
""" Get a canvas's dirty rectangle. Return python dictionnary with
coords as keys: x, y, width, height.
idx -- the requested rectangle index
"""
dct = None
x = ctypes.c_int()
y = ctypes.c_int()
width = ctypes.c_int()
height = ctypes.c_int()
_lib.caca_get_dirty_rect.argtypes = [
_Canvas, ctypes.c_int,
ctypes.POINTER(ctypes.c_int), ctypes.POINTER(ctypes.c_int),
ctypes.POINTER(ctypes.c_int), ctypes.POINTER(ctypes.c_int)
]
_lib.caca_get_dirty_rect.restype = ctypes.c_int
try:
ret = _lib.caca_get_dirty_rect(self, idx, x, y, width, height)
except ctypes.ArgumentError:
raise CanvasError("Specified rectangle index is invalid")
else:
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Specified rectangle index is out of"
" bounds")
else:
dct = {
'x': x.value, 'y': y.value,
'width': width.value, 'height': height.value,
}
return dct
def add_dirty_rect(self, x, y, width, height):
""" Add an area to the canvas's dirty rectangle list.
x -- the leftmost edge of the additional dirty rectangle
y -- the topmost edge of the additional dirty rectangle
width -- the width of the additional dirty rectangle
height -- the height of the additional dirty rectangle
"""
_lib.caca_add_dirty_rect.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int
]
_lib.caca_add_dirty_rect.restype = ctypes.c_int
try:
ret =_lib.caca_add_dirty_rect(self, x, y, width, height)
except ctypes.ArgumentError:
raise CanvasError("Specified coordinate or size is invalid")
else:
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Specified rectangle coordinates are out"
" of bounds")
else:
return ret
def remove_dirty_rect(self, x, y, width, height):
""" Remove an area from the dirty rectangle list.
x -- the leftmost edge of the additional dirty rectangle
y -- the topmost edge of the additional dirty rectangle
width -- the width of the additional rectangle
height -- the height of the additional dirty rectangle
"""
_lib.caca_remove_dirty_rect.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int
]
_lib.caca_remove_dirty_rect.restype = ctypes.c_int
try:
ret = _lib.caca_remove_dirty_rect(self, x, y, width, height)
except ctypes.ArgumentError:
raise CanvasError("Specified coordinate or size is invalid")
else:
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Specified rectangle coordinates are out"
" of bounds")
else:
return ret
def clear_dirty_rect_list(self):
""" Clear a canvas's dirty rectangle list.
"""
_lib.caca_clear_dirty_rect_list.argtypes = [_Canvas]
_lib.caca_clear_dirty_rect_list.restype = ctypes.c_int
return _lib.caca_clear_dirty_rect_list(self)
def invert(self):
""" Invert a canvas' colours.
"""
_lib.caca_invert.argtypes = [_Canvas]
_lib.caca_invert.restype = ctypes.c_int
return _lib.caca_invert(self)
def flip(self):
""" Flip a canvas horizontally.
"""
_lib.caca_flip.argtypes = [_Canvas]
_lib.caca_flip.restype = ctypes.c_int
return _lib.caca_flip(self)
def flop(self):
""" Flip a canvas vertically.
"""
_lib.caca_flop.argtypes = [_Canvas]
_lib.caca_flop.restype = ctypes.c_int
return _lib.caca_flop(self)
def rotate_180(self):
""" Rotate a canvas.
"""
_lib.caca_rotate_180.argtypes = [_Canvas]
_lib.caca_rotate_180.restype = ctypes.c_int
return _lib.caca_rotate_180(self)
def rotate_left(self):
""" Rotate a canvas, 90 degrees counterclockwise.
"""
_lib.caca_rotate_left.argtypes = [_Canvas]
_lib.caca_rotate_left.restype = ctypes.c_int
ret = _lib.caca_rotate_left(self)
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EBUSY:
raise CanvasError("The canvas is in use by a display driver"
" and cannot be rotated")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate the new"
" canvas size")
else:
return ret
def rotate_right(self):
""" Rotate a canvas, 90 degrees clockwise.
"""
_lib.caca_rotate_right.argtypes = [_Canvas]
_lib.caca_rotate_right.restype = ctypes.c_int
ret = _lib.caca_rotate_right(self)
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EBUSY:
raise CanvasError("The canvas is in use by a display driver"
" and cannot be rotated")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate the new"
" canvas size")
else:
return ret
def stretch_left(self):
""" Rotate and stretch a canvas, 90 degrees counterclockwise.
"""
_lib.caca_stretch_left.argtypes = [_Canvas]
_lib.caca_stretch_left.restype = ctypes.c_int
ret = _lib.caca_stretch_left(self)
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EBUSY:
raise CanvasError("The canvas is in use by a display driver"
" and cannot be rotated")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate the new"
" canvas size")
else:
return ret
def stretch_right(self):
""" Rotate and stretch a canvas, 90 degrees clockwise.
"""
_lib.caca_stretch_right.argtypes = [_Canvas]
_lib.caca_stretch_right.restype = ctypes.c_int
ret = _lib.caca_stretch_right(self)
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EBUSY:
raise CanvasError("The canvas is in use by a display driver"
" and cannot be rotated")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate the new"
" canvas size")
else:
return ret
def get_attr(self, x, y):
""" Get the text attribute at the given coordinates.
x -- X coordinate
y -- Y coordinate
"""
_lib.caca_get_attr.argtypes = [_Canvas, ctypes.c_int, ctypes.c_int]
_lib.caca_get_attr.restype = ctypes.c_uint32
try:
ret = _lib.caca_get_attr(self, x, y)
except ctypes.ArgumentError:
raise CanvasError("Specified coordinate X or Y is invalid")
else:
return ret
def set_attr(self, attr):
""" Set the default character attribute.
attr -- the requested attribute value
"""
_lib.caca_set_attr.argtypes = [_Canvas, ctypes.c_uint32]
_lib.caca_set_attr.restype = ctypes.c_int
try:
ret = _lib.caca_set_attr(self, attr)
except ctypes.ArgumentError:
raise CanvasError("Specified attribute is invalid")
else:
return ret
def unset_attr(self, attr):
""" Unset the default character attribute.
attr -- the requested attribute value
"""
_lib.caca_unset_attr.argtypes = [_Canvas, ctypes.c_uint32]
_lib.caca_unset_attr.restype = ctypes.c_int
try:
ret = _lib.caca_unset_attr(self, attr)
except ctypes.ArgumentError:
raise CanvasError("Specified attribute is invalid")
else:
return ret
def toggle_attr(self, attr):
""" Toggle the default character attribute.
attr -- the requested attribute value
"""
_lib.caca_toggle_attr.argtypes = [_Canvas, ctypes.c_uint32]
_lib.caca_toggle_attr.restype = ctypes.c_int
try:
ret = _lib.caca_toggle_attr(self, attr)
except ctypes.ArgumentError:
raise CanvasError("Specified attribute is invalid")
else:
return ret
def put_attr(self, x, y, attr):
""" Set the character attribute at the given coordinates.
x -- X coordinate
y -- Y coordinate
attr -- the requested attribute value
"""
_lib.caca_put_attr.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, ctypes.c_uint32
]
_lib.caca_put_attr.restype = ctypes.c_int
try:
ret = _lib.caca_put_attr(self, x, y, attr)
except ctypes.ArgumentError:
raise CanvasError("Specified coordinate or attribute is invalid")
else:
return ret
def set_color_ansi(self, fg, bg):
""" Set the default colour pair for text (ANSI version).
fg -- the requested ANSI foreground colour.
bg -- the requested ANSI background colour.
"""
_lib.caca_set_color_ansi.argtypes = [
_Canvas, ctypes.c_uint8, ctypes.c_uint8
]
_lib.caca_set_color_ansi.restype = ctypes.c_int
try:
ret = _lib.caca_set_color_ansi(self, fg, bg)
except ctypes.ArgumentError:
raise CanvasError("At least one of the colour values is invalid")
else:
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("At least one of the colour values"
" is invalid")
else:
return ret
def set_color_argb(self, fg, bg):
""" Set the default colour pair for text (truecolor version).
fg -- the requested ARGB foreground colour.
bg -- the requested ARGB background colour.
"""
_lib.caca_set_color_argb.argtypes = [
_Canvas, ctypes.c_uint16, ctypes.c_uint16
]
_lib.caca_set_color_argb.restype = ctypes.c_int
try:
ret = _lib.caca_set_color_argb(self, fg, bg)
except ctypes.ArgumentError:
raise CanvasError("At least one of the colour values is invalid")
else:
return ret
def draw_line(self, x1, y1, x2, y2, ch):
""" Draw a line on the canvas using the given character.
x1 -- X coordinate of the first point
y1 -- Y coordinate of the first point
x2 -- X coordinate of the second point
y2 -- Y coordinate of the second point
ch -- character to be used to draw the line
"""
_lib.caca_draw_line.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int, ctypes.c_uint32
]
_lib.caca_draw_line.restype = ctypes.c_int
if not isinstance(ch, str):
raise CanvasError("Specified character is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
try:
ret = _lib.caca_draw_line(self, x1, y1, x2, y2, ch)
except ctypes.ArgumentError:
raise CanvasError("specified coordinate is invalid")
else:
return ret
def draw_polyline(self, array_xy, ch):
""" Draw a polyline.
array_xy -- List of (X, Y) coordinates
ch -- character to be used to draw the line
"""
if not isinstance(array_xy, list) or len(array_xy) < 2:
raise CanvasError("Specified array of coordinates is invalid")
else:
for item in array_xy:
if not isinstance(item, list) and \
not isinstance(item, tuple):
raise CanvasError("Specified array of coordinates"
" is invalid")
ax = ctypes.c_int * len(array_xy)
ay = ctypes.c_int * len(array_xy)
_lib.caca_draw_polyline.argtypes = [
_Canvas, ax, ay, ctypes.c_int, ctypes.c_uint32
]
_lib.caca_draw_polyline.restype = ctypes.c_int
if not isinstance(ch, str):
raise CanvasError("Specified character is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
try:
ax = ax(*[x[0] for x in array_xy])
ay = ay(*[y[1] for y in array_xy])
except IndexError:
raise CanvasError("Specified array coordinates is invalid")
try:
ret = _lib.caca_draw_polyline(self, ax, ay,
len(array_xy) - 1, ch)
except ctypes.ArgumentError:
raise CanvasError("specified array of coordinates is invalid")
else:
return ret
def draw_thin_line(self, x1, y1, x2, y2):
""" Draw a thin line on the canvas, using ASCII art.
x1 -- X coordinate of the first point
y1 -- Y coordinate of the first point
x2 -- X coordinate of the second point
y2 -- Y coordinate of the second point
"""
_lib.caca_draw_thin_line.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int
]
_lib.caca_draw_thin_line.restype = ctypes.c_int
try:
ret = _lib.caca_draw_thin_line(self, x1, y1, x2, y2)
except ctypes.ArgumentError:
raise CanvasError("specified coordinate is invalid")
else:
return ret
def draw_thin_polyline(self, array_xy):
""" Draw an ASCII art thin polyline.
array_xy -- Array of (X, Y) coordinates
"""
if not isinstance(array_xy, list) or len(array_xy) < 2:
raise CanvasError("Specified array of coordinates is invalid")
else:
for item in array_xy:
if not isinstance(item, list) and \
not isinstance(item, tuple):
raise CanvasError("Specified array of coordinates"
" is invalid")
ax = ctypes.c_int * len(array_xy)
ay = ctypes.c_int * len(array_xy)
_lib.caca_draw_thin_polyline.argtypes = [
Canvas, ax, ay, ctypes.c_int
]
_lib.caca_draw_thin_polyline.restype = ctypes.c_int
try:
ax = ax(*[x[0] for x in array_xy])
ay = ay(*[y[1] for y in array_xy])
except IndexError:
raise CanvasError("Specified array coordinates is invalid")
try:
ret = _lib.caca_draw_thin_polyline(self, ax, ay, len(array_xy) - 1)
except ctypes.ArgumentError:
raise CanvasError("specified array of coordinates is invalid")
else:
return ret
def draw_circle(self, x, y, r, ch):
""" Draw a circle on the canvas using the given character.
x -- center X coordinate
y -- center Y coordinate
r -- circle radius
ch -- the UTF-32 character to be used to draw the circle outline
"""
_lib.caca_draw_circle.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, ctypes.c_int, ctypes.c_uint32
]
_lib.caca_draw_circle.restype = ctypes.c_int
if not isinstance(ch, str):
raise CanvasError("Specified character is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
try:
ret = _lib.caca_draw_circle(self, x, y, r, ch)
except ctypes.ArgumentError:
raise CanvasError("Specified circle coordinate or radius is"
" invalid")
else:
return ret
def draw_ellipse(self, xo, yo, a, b, ch):
""" Draw an ellipse on the canvas using the given character.
xo -- center X coordinate
yo -- center Y coordinate
a -- ellipse x radius
b -- ellipse y radius
ch -- UTF-32 character to be used to draw the ellipse outline
"""
_lib.caca_draw_ellipse.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int, ctypes.c_uint32
]
_lib.caca_draw_ellipse.restype = ctypes.c_int
if not isinstance(ch, str):
raise CanvasError("Specified character is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
try:
ret = _lib.caca_draw_ellipse(self, xo, yo, a, b, ch)
except ctypes.ArgumentError:
raise CanvasError("Specified ellipse coordinate or radius is"
" invalid")
else:
return ret
def draw_thin_ellipse(self, xo, yo, a, b):
""" Draw a thin ellipse on the canvas.
xo -- center X coordinate
yo -- center Y coordinate
a -- ellipse X radius
b -- ellipse Y radius
"""
_lib.caca_draw_thin_ellipse.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int
]
_lib.caca_draw_thin_ellipse.restype = ctypes.c_int
try:
ret = _lib.caca_draw_thin_ellipse(self, xo, yo, a, b)
except ctypes.ArgumentError:
raise CanvasError("Specified ellipse coordinate or radius is"
" invalid")
else:
return ret
def fill_ellipse(self, xo, yo, a, b, ch):
""" Fill an ellipse on the canvas using the given character.
xo -- center X coordinate
yo -- center Y coordinate
a -- ellipse X radius
b -- ellipse Y radius
ch -- UTF-32 character to be used to fill the ellipse
"""
_lib.caca_fill_ellipse.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int, ctypes.c_uint32
]
_lib.caca_fill_ellipse.restype = ctypes.c_int
if not isinstance(ch, str):
raise CanvasError("Specified character is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
try:
ret = _lib.caca_fill_ellipse(self, xo, yo, a, b, ch)
except ctypes.ArgumentError:
raise CanvasError("Specified ellipse coordinate or radius is"
" invalid")
else:
return ret
def draw_box(self, x, y, width, height, ch):
""" Draw a box on the canvas using the given character.
x -- X coordinate of the upper-left corner of the box
y -- Y coordinate of the upper-left corner of the box
width -- width of the box
height -- height of the box
ch -- character to be used to draw the box
"""
_lib.caca_draw_box.argtypes = [
Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int, ctypes.c_uint32
]
_lib.caca_draw_box.restype = ctypes.c_int
if not isinstance(ch, str):
raise CanvasError("Specified character is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
try:
ret = _lib.caca_draw_box(self, x, y, width, height, ch)
except ctypes.ArgumentError:
raise CanvasError("specified box coordinate is invalid")
else:
return ret
def draw_thin_box(self, x, y, width, height):
""" Draw a thin box on the canvas.
x -- X coordinate of the upper-left corner of the box
y -- Y coordinate of the upper-left corner of the box
width -- width of the box
height -- height of the box
"""
_lib.caca_draw_thin_box.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int
]
_lib.caca_draw_thin_box.restype = ctypes.c_int
try:
ret = _lib.caca_draw_thin_box(self, x, y, width, height)
except ctypes.ArgumentError:
raise CanvasError("specified box coordinate is invalid")
else:
return ret
def draw_cp437_box(self, x, y, width, height):
""" Draw a box on the canvas using CP437 characters.
x -- X coordinate of the upper-left corner box
y -- Y coordinate of the upper-left corner box
width -- width of the box
height -- height of the box
"""
_lib.caca_draw_cp437_box.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int
]
_lib.caca_draw_cp437_box.restype = ctypes.c_int
try:
ret = _lib.caca_draw_cp437_box(self, x, y, width, height)
except ctypes.ArgumentError:
raise CanvasError("specified box coordinate is invalid")
else:
return ret
def fill_box(self, x, y, width, height, ch):
""" Fill a box on the canvas using the given character.
x -- X coordinate of the upper-left corner of the box
y -- Y coordinate of the upper-left corner of the box
width -- width of the box
height -- height of the box
ch -- UFT-32 character to be used to fill the box
"""
_lib.caca_fill_box.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int, ctypes.c_uint32
]
_lib.caca_fill_box.restype = ctypes.c_int
if not isinstance(ch, str):
raise CanvasError("Specified character is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
try:
ret = _lib.caca_fill_box(self, x, y, width, height, ch)
except ctypes.ArgumentError:
raise CanvasError("specified box coordinate is invalid")
else:
return ret
def draw_triangle(self, x1, y1, x2, y2, x3, y3, ch):
""" Draw a triangle on the canvas using the given character.
x1 -- X coordinate of the first point
y1 -- Y coordinate of the first point
x2 -- X coordinate of the second point
y2 -- Y coordinate of the second point
x3 -- X coordinate of the third point
y3 -- Y coordinate of the third point
ch -- UTF-32 character to be used to draw the triangle outline
"""
_lib.caca_draw_triangle.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int, ctypes.c_int, ctypes.c_uint32
]
_lib.caca_draw_triangle.restype = ctypes.c_int
if not isinstance(ch, str):
raise CanvasError("Specified character is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
try:
ret = _lib.caca_draw_triangle(self, x1, y1, x2, y2, x3, y3, ch)
except ctypes.ArgumentError:
raise CanvasError("specified triangle coordinate is invalid")
else:
return ret
def draw_thin_triangle(self, x1, y1, x2, y2, x3, y3):
""" Draw a thin triangle on the canvas.
x1 -- X coordinate of the first point
y1 -- Y coordinate of the first point
x2 -- X coordinate of the second point
y2 -- Y coordinate of the second point
x3 -- X coordinate of the third point
y3 -- Y coordinate of the third point
"""
_lib.caca_draw_thin_triangle.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int, ctypes.c_int
]
_lib.caca_draw_thin_triangle.restype = ctypes.c_int
try:
ret = _lib.caca_draw_thin_triangle(self, x1, y1, x2, y2, x3, y3)
except ctypes.ArgumentError:
raise CanvasError("specified triangle coordinate is invalid")
else:
return ret
def fill_triangle(self, x1, y1, x2, y2, x3, y3, ch):
""" Fill a triangle on the canvas using the given character.
x1 -- X coordinate of the first point
y1 -- Y coordinate of the first point
x2 -- X coordinate of the second point
y2 -- Y coordinate of the second point
x3 -- X coordinate of the second point
y3 -- Y coordinate of the second point
ch -- UTF-32 character to be used to fill the triangle
"""
_lib.caca_fill_triangle.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_int, ctypes.c_int
]
_lib.caca_fill_triangle.restype = ctypes.c_int
if not isinstance(ch, str):
raise CanvasError("Specified character is invalid")
else:
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
try:
ret = _lib.caca_fill_triangle(self, x1, y1, x2, y2, x3, y3, ch)
except ctypes.ArgumentError:
raise CanvasError("specified triangle coordinate is invalid")
else:
return ret
def fill_triangle_textured(self, coords, tex, uv):
""" Fill a triangle on the canvas using an arbitrary-sized texture.
coords -- coordinates of the triangle (3{x,y})
tex -- the handle of the canvas texture
uv -- coordinates of the texture (3{u,v})
"""
_lib.caca_fill_triangle_textured.argtypes = [
_Canvas, ctypes.c_int * 6, _Canvas, ctypes.c_int * 6
]
_lib.caca_fill_triangle_textured.restype = ctypes.c_int
return _lib.caca_fill_triangle_textured(self, coords, tex, uv)
def get_frame_count(self):
""" Get the number of frames in a canvas.
"""
_lib.caca_get_frame_count.argtypes = [_Canvas]
_lib.caca_get_frame_count.restype = ctypes.c_int
return _lib.caca_get_frame_count(self)
def set_frame(self, idx):
""" Activate a given canvas frame.
idx -- the canvas frame to activate
"""
_lib.caca_set_frame.argtypes = [_Canvas, ctypes.c_int]
_lib.caca_set_frame.restype = ctypes.c_int
try:
ret = _lib.caca_set_frame(self, idx)
except ctypes.ArgumentError:
raise CanvasError("specified index is invalid")
else:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Requested frame is out of range")
else:
return ret
def get_frame_name(self):
""" Get the current frame's name.
"""
_lib.caca_get_frame_name.argtypes = [_Canvas]
_lib.caca_get_frame_name.restype = ctypes.c_char_p
if _PYTHON3:
return _bytes_to_str(_lib.caca_get_frame_name(self))
else:
return _lib.caca_get_frame_name(self)
def set_frame_name(self, name):
""" Set the current frame's name.
name -- the name to give to the current frame
"""
_lib.caca_set_frame_name.argtypes = [_Canvas, ctypes.c_char_p]
_lib.caca_set_frame_name.restype = ctypes.c_int
if _PYTHON3 and isinstance(name, str):
name = _str_to_bytes(name)
try:
ret = _lib.caca_set_frame_name(self, name)
except ctypes.ArgumentError:
raise CanvasError("Specified name is invalid")
else:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate new frame")
else:
return ret
def create_frame(self, idx):
""" Add a frame to a canvas.
idx -- the index where to insert the new frame
"""
_lib.caca_create_frame.argtypes = [_Canvas, ctypes.c_int]
_lib.caca_create_frame.restype = ctypes.c_int
try:
ret = _lib.caca_create_frame(self, idx)
except ctypes.ArgumentError:
raise CanvasError("specified index is invalid")
else:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate new frame")
else:
return ret
def free_frame(self, idx):
""" Remove a frame from a canvas.
idx -- the index of the frame to delete
"""
_lib.caca_free_frame.argtypes = [_Canvas, ctypes.c_int]
_lib.caca_free_frame.restype = ctypes.c_int
try:
ret = _lib.caca_free_frame(self, idx)
except ctypes.ArgumentError:
raise CanvasError("specified index is invalid")
else:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Requested frame is out of range, or attempt"
" to delete the last frame of the canvas")
else:
return ret
def import_from_memory(self, data, fmt):
""" Import a memory buffer into a canvas.
data -- a memory area containing the data to be loaded into
the canvas
fmt -- a string describing the input format
Valid values for format are:
- "": attempt to autodetect the file format.
- caca: import native libcaca files.
- text: import ASCII text files.
- ansi: import ANSI files.
- utf8: import UTF-8 files with ANSI colour codes.
"""
_lib.caca_import_canvas_from_memory.argtypes = [
Canvas, ctypes.c_char_p,
ctypes.c_size_t, ctypes.c_char_p
]
_lib.caca_import_canvas_from_memory.restype = ctypes.c_int
if _PYTHON3 and isinstance(data, str):
data = _str_to_bytes(data)
if _PYTHON3 and isinstance(fmt, str):
fmt = _str_to_bytes(fmt)
length = ctypes.c_size_t(len(data))
try:
ret = _lib.caca_import_canvas_from_memory(self, data, length, fmt)
except ctypes.ArgumentError:
raise CanvasError("Given data are invalid")
else:
err = ctypes.c_int.in_dll(_lib, "errno")
if ret == -1:
if err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate canvas")
elif err.value == errno.EINVAL:
raise CanvasError("Invalid format requested")
else:
return ret
def import_from_file(self, filename, fmt):
""" Import a file into a canvas.
filename -- the name of the file to load
fmt -- a string describing the input format
Valid values for format are:
- "": attempt to autodetect the file format.
- caca: import native libcaca files.
- text: import ASCII text files.
- ansi: import ANSI files.
- utf8: import UTF-8 files with ANSI colour codes.
"""
_lib.caca_import_canvas_from_file.argtypes = [
_Canvas, ctypes.c_char_p, ctypes.c_char_p
]
_lib.caca_import_canvas_from_file.restype = ctypes.c_int
if _PYTHON3 and isinstance(filename, str):
filename = _str_to_bytes(filename)
if _PYTHON3 and isinstance(fmt, str):
fmt = _str_to_bytes(fmt)
try:
ret = _lib.caca_import_canvas_from_file(self, filename, fmt)
except ctypes.ArgumentError:
raise CanvasError("Specified filename is invalid")
else:
err = ctypes.c_int.in_dll(_lib, "errno")
if ret == -1:
if err.value == errno.ENOSYS:
raise CanvasError("File access is not implemented on this"
" system")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate canvas")
elif err.value == errno.EINVAL:
raise CanvasError("Invalid format requested")
else:
return ret
def import_area_from_memory(self, x, y, data, fmt):
""" Import a memory buffer into a canvas area.
x -- the leftmost coordinate of the area to import to
y -- the topmost coordinate of the area to import to
data -- a memory area containing the data to be loaded into
the canvas
fmt -- a string describing the input format
Valid values for format are:
- "": attempt to autodetect the file format.
- caca: import native libcaca files.
- text: import ASCII text files.
- ansi: import ANSI files.
- utf8: import UTF-8 files with ANSI colour codes.
"""
length = ctypes.c_size_t(len(data))
_lib.caca_import_area_from_memory.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_char_p, ctypes.c_size_t, ctypes.c_char_p
]
_lib.caca_import_area_from_memory.restype = ctypes.c_int
if _PYTHON3 and isinstance(data, str):
data = _str_to_bytes(data)
if _PYTHON3 and isinstance(fmt, str):
fmt = _str_to_bytes(fmt)
try:
ret = _lib.caca_import_area_from_memory(self, x, y,
data, length, fmt)
except ctypes.ArgumentError:
raise CanvasError("Specified coordinate X or Y is invalid")
else:
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Unsupported format requested or"
" invalid coordinates")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate canvas")
else:
return ret
def import_area_from_file(self, x, y, filename, fmt):
""" Import a file into a canvas area.
x -- the leftmost coordinate of the area to import to
y -- the topmost coordinate of the area to import to
filename -- the name of the file to be load
fmt -- a string describing the input format
Valid values for format are:
- "": attempt to autodetect the file format.
- caca: import native libcaca files.
- text: import ASCII text files.
- ansi: import ANSI files.
- utf8: import UTF-8 files with ANSI colour codes.
"""
_lib.caca_import_area_from_file.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int,
ctypes.c_char_p, ctypes.c_char_p
]
_lib.caca_import_area_from_file.restype = ctypes.c_int
if _PYTHON3 and isinstance(filename, str):
filename = _str_to_bytes(filename)
if _PYTHON3 and isinstance(fmt, str):
fmt = _str_to_bytes(fmt)
try:
ret = _lib.caca_import_area_from_file(self, x, y, filename, fmt)
except ctypes.ArgumentError:
raise CanvasError("Specified coordinate X or Y is invalid")
else:
if ret == -1:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.ENOSYS:
raise CanvasError("File access is not implemented on this"
" system")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate canvas")
elif err.value == errno.EINVAL:
raise CanvasError("Unsupported format requested or"
" invalid coordinates")
else:
return ret
def export_to_memory(self, fmt):
""" Export a canvas into a foreign format.
fmt -- a string describing the output format
Valid values for format are:
- caca: export native libcaca files.
- ansi: export ANSI art (CP437 charset with ANSI colour codes).
- html: export an HTML page with CSS information.
- html3: export an HTML table that should be compatible with
most navigators, including textmode ones.
- irc: export UTF-8 text with mIRC colour codes.
- ps: export a PostScript document.
- svg: export an SVG vector image.
- tga: export a TGA image.
"""
p_size_t = ctypes.POINTER(ctypes.c_size_t)
_lib.caca_export_canvas_to_memory.argtypes = [
_Canvas, ctypes.c_char_p, p_size_t
]
_lib.caca_export_canvas_to_memory.restype = ctypes.POINTER(
ctypes.c_char_p)
p = ctypes.c_size_t()
if _PYTHON3 and isinstance(fmt, str):
fmt = _str_to_bytes(fmt)
try:
ret = _lib.caca_export_canvas_to_memory(self, fmt, p)
except ctypes.ArgumentError:
raise CanvasError("Invalid format requested")
else:
if not ret:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Invalid format requested")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate output"
" buffer")
else:
if _PYTHON3:
return _bytes_to_str(ctypes.string_at(ret, p.value))
else:
return ctypes.string_at(ret, p.value)
def export_area_to_memory(self, x, y, width, height, fmt):
""" Export a canvas portion into a foreign format.
x -- the leftmost coordinate of the area to export
y -- the topmost coordinate of the area to export
width -- the width of the area to export
height -- the height of the area to export
fmt -- a string describing the output format
Valid values for format are:
- caca: export native libcaca files.
- ansi: export ANSI art (CP437 charset with ANSI colour codes).
- html: export an HTML page with CSS information.
- html3: export an HTML table that should be compatible with
most navigators, including textmode ones.
- irc: export UTF-8 text with mIRC colour codes.
- ps: export a PostScript document.
- svg: export an SVG vector image.
- tga: export a TGA image.
"""
p_size_t = ctypes.POINTER(ctypes.c_size_t)
_lib.caca_export_area_to_memory.argtypes = [
_Canvas, ctypes.c_int, ctypes.c_int, ctypes.c_int,
ctypes.c_int, ctypes.c_char_p, p_size_t
]
_lib.caca_export_area_to_memory.restype = ctypes.POINTER(ctypes.c_char_p)
p = ctypes.c_size_t()
if _PYTHON3 and isinstance(fmt, str):
fmt = _str_to_bytes(fmt)
try:
ret = _lib.caca_export_area_to_memory(self, x, y, width, height,
fmt, p)
except ctypes.ArgumentError:
raise CanvasError("Requested area coordinate is invalid")
else:
if not ret:
err = ctypes.c_int.in_dll(_lib, "errno")
if err.value == errno.EINVAL:
raise CanvasError("Invalid format requested")
elif err.value == errno.ENOMEM:
raise CanvasError("Not enough memory to allocate output"
" buffer")
else:
if _PYTHON3:
return _bytes_to_str(ctypes.string_at(ret, p.value))
else:
return ctypes.string_at(ret, p.value)
def set_figfont(self, filename):
""" Load a figfont and attach it to a canvas.
filename -- the figfont file to load.
"""
_lib.caca_canvas_set_figfont.argtypes = [_Canvas, ctypes.c_char_p]
_lib.caca_canvas_set_figfont.restype = ctypes.c_int
if _PYTHON3 and isinstance(filename, str):
filename = _str_to_bytes(filename)
return _lib.caca_canvas_set_figfont(self, filename)
def put_figchar(self, ch):
""" Paste a character using the current figfont.
ch -- the character to paste
"""
_lib.caca_put_figchar.argtypes = [_Canvas, ctypes.c_uint32]
_lib.caca_put_figchar.restype = ctypes.c_int
if _PYTHON3 and isinstance(ch, str):
ch = _str_to_bytes(ch)
try:
ch = ord(ch)
except TypeError:
ch = utf8_to_utf32(ch)
return _lib.caca_put_figchar(self, ch)
def flush_figlet(self):
""" Flush the figlet context
"""
_lib.caca_flush_figlet.argtypes = [_Canvas]
_lib.caca_flush_figlet.restype = ctypes.c_int
return _lib.caca_flush_figlet(self)
def render(self, font, buf, width, height, pitch):
""" Render the canvas onto an image buffer.
font -- a Font() object
buf -- the image buffer
width -- the width (in pixels) of the image
heigth -- the height (in pixels) of the image
pitch -- the pitch (in bytes) of the image
"""
_lib.caca_render_canvas.argtypes = [
_Canvas, _Font, ctypes.c_char_p,
ctypes.c_int, ctypes.c_int, ctypes.c_int
]
_lib.caca_render_canvas.restype = ctypes.c_int
return _lib.caca_render_canvas(self, font, buf, width, height, pitch)
class NullCanvas(_Canvas):
""" Represent a NULL canvas_t, eg to use as canvas mask for blit operations.
"""
def __str__(self):
return "<NullCanvas>"
class CanvasError(Exception):
pass